Android Test - Espresso 延迟匹配的实现

Espresso 会检测主线程何时处于空闲状态，以便可以在适当的时间运行测试命令，从而提高测试的可靠性。

先上示例代码：来自官网

    @Test
    fun greeterSaysHello() {
        onView(withId(R.id.name_field)).perform(typeText("Steve"))
        onView(withId(R.id.greet_button)).perform(click())
        onView(withText("Hello Steve!")).check(matches(isDisplayed()))
    }
    

很简单的代码。
场景：如果按钮 greet_button 的点击事件触发后，“Hello Steve!” 文本将在访问接口后才会显示，这个时间是不确定性的，所以给它添加 Thread.sleep() 也就不可行了。

空闲资源：

Espresso的空闲资源表示结果会影响界面测试中后续操作的异步操作。通过向 Espresso 注册空闲资源，您可以在测试应用时更可靠地验证这些异步操作。

⚠️ 这里我们虽然可以使用Espresso空闲资源来处理（使用 IdlingRegistry 类），但是 应用的生产代码中存在空闲资源逻辑，这是不推荐的。

处理方案：

根据如下匹配方法： ViewAssertions.matches() 

  public static ViewAssertion matches(final Matcher viewMatcher) {
    return new MatchesViewAssertion(checkNotNull(viewMatcher));
  }

重写 MatchesViewAssertion() ：

class WaitingNotMatchViewException(override val message: String) : RuntimeException()


// 简便易使用
fun waitMatches(viewMatcher: Matcher): ViewAssertion {
    return WaitMatchesViewAssertion(checkNotNull(viewMatcher))
}


@VisibleForTesting
class WaitMatchesViewAssertion(private val viewMatcher: Matcher) : ViewAssertion {

    private val TAG = WaitMatchesViewAssertion::class.java.simpleName

    override fun check(view: View?, noViewException: NoMatchingViewException?) {
        val description = StringDescription()
        description.appendText("'")
        viewMatcher.describeTo(description)
        if (noViewException != null) {
            description.appendText(
                String.format(
                    Locale.ROOT,
                    "' check could not be performed because view '%s' was not found.n",
                    noViewException.viewMatcherDescription
                )
            )
            Log.e(TAG, description.toString())
            throw noViewException
        } else {
            // 添加 try-catch
            try {
                description.appendText("' doesn't match the selected view.")
                ViewMatchers.assertThat(description.toString(), view, viewMatcher)
            }catch (e: AssertionFailedError){
                // 抛出异常 WaitingNotMatchViewException
                throw WaitingNotMatchViewException("doesn't match the selected view.")
            }
        }
    }

    override fun toString(): String {
        return String.format(Locale.ROOT, "MatchesViewAssertion{viewMatcher=%s}", viewMatcher)
    }
}

封装：

fun waitForElementWithMatcher(
    elementToCheck: ViewInteraction, // 要检查的元素
    viewMatcher: Matcher, // 匹配项
    secondsToWait: Int = 30  // 超时时间
) {
    var i = 0
    var elementMatched = false
    while (i <= secondsToWait) {
        if (IntegrationUtil.waitElementToViewMatcher(elementToCheck, viewMatcher)) {
            elementMatched = true
            break
        }
        Thread.sleep(1000)  // 这里的时间可以自己设定
        i++
    }
    if (!elementMatched) {
        throw Exception("Expected to find the element on Screen .Waited for $i seconds")
    }
}



fun waitElementToViewMatcher(
    elementToCheck: ViewInteraction,
    viewMatcher: Matcher
): Boolean {
    try {
        val elementList = mutableListOf(elementToCheck.check(waitMatches(viewMatcher)))
        if (elementList.count() == 1)
            return true
    } catch (e: NoMatchingViewException) {
        return false
    } catch (e: WaitingNotMatchViewException) {
        return false
    } catch (e: Exception) {
        throw Exception(e.message)
    }
    return false
}

使用：

    @Test
    fun greeterSaysHello() {
        onView(withId(R.id.name_field)).perform(typeText("Steve"))
        onView(withId(R.id.greet_button)).perform(click())
        // onView(withText("Hello Steve!")).check(matches(isDisplayed()))
        waitForElementWithMatcher(onView(withText("Hello Steve!")), isDisplayed(), 30)
    }
    

最后，欢迎讨论。